arXiv subjects

Alex de Lozanne

Publications and source records attributed to Alex de Lozanne.

5 recordsLinked to original sources

arXiv2018

Imaging the magnetic states in an actinide ferromagnet UMn$_2$Ge$_2$

We present studies of the magnetic domain structure of UMn$_2$Ge$_2$ single crystals using a home-built low temperature magnetic force microscope. The material has two distinct magnetic ordering temperatures, originating from the Mn and U moments. At room temperature, where the Mn moments dominate, there are flower-like domain patterns similar to those observed in uniaxial ferromagnets. After exposing the sample to a one-tesla magnetic field near 40 K, the evolution of the magnetic domains are imaged through zero-field warming up to 200 K. Near the ordering temperature of the uranium moments a clear change in the domain wall motion is observed. The domain size analysis of the flower-like pattern reveals that the domain structure is consistent with a model of branching domains.

cond-mat.mtrl-sci↗

arXiv2015

Magnetic domain tuning and the emergence of bubble domains in the bilayer manganite La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ (x=0.32)

We report a magnetic force microscopy study of the magnetic domain evolution in the layered manganite La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ (with $x=0.32$). This strongly correlated electron compound is known to exhibit a wide range of magnetic phases, including a recently uncovered biskyrmion phase. We observe a continuous transition from dendritic to stripe-like domains, followed by the formation of magnetic bubbles due to a field- and temperature dependent competition between in-plane and out-of-plane spin alignments. The magnetic bubble phase appears at comparable field- and temperature ranges as the biskyrmion phase, suggesting a close relation between both phases. Based on our real-space images we construct a temperature-field phase diagram for this composition.

cond-mat.str-el↗

arXiv2013

Honeycomb lattice of graphite probed by scanning tunneling microscopy with a carbon nanotube tip

A carbon nanotube (CNT) tip was fabricated at the apex of an etched tungsten wire by chemical vapor deposition and used for scanning tunneling microscopy. The honeycomb lattice of graphite in the STM images was resolved with a CNT tip at T=79 K. The superior spatial resolution originating from the p orbitals of a CNT is responsible for the image of the honeycomb lattice of graphite in the STM images. The CNT tips are useful to image samples whose lattice constants are small and to get orbital information in samples with orbital ordering due to their superior spatial resolution with the sharp p orbitals.

cond-mat.mes-hall↗

arXiv2013

Observation of electronic inhomogeneity and charge density wave in a bilayer La$_{1.36}$Sr$_{1.64}$Mn$_2$O$_7$ single crystal

We employed a scanning tunneling microscope to image the (001) surface topography and local density of states (LDOS) in La$_{2-2x}$Sr$_{1+2x}$Mn$_2$O$_7$ (x=0.32, LSMO) single crystals below the Curie temperature (T$_C$ = 120 K). The LDOS maps revealed a stripe-like modulation propagating along the tetragonal a axis with a wavelength of about 1.6 Å, which is indicative of a charge density wave (CDW). The observed CDW in the x=0.32 sample is far from the Fermi surface nesting instability as compared with the data of angle resolved photoemission spectroscopy in an x=0.40 sample. The stripe model developed previously for cuprates can explain the observed CDW in our LSMO sample, indicating that competing interactions between localized and itinerant phases are the origin of the spatial modulations present intrinsically in cuprates and manganites.

cond-mat.str-el↗

arXiv2010

Seeing Quantum Fractals

This Perspectives article highlights some of the interesting features and open questions presented by recent scanning tunneling microscope (STM) experiments on GaMnAs near the metal-insulator transition.

cond-mat.mes-hall↗